1. Field of the Invention
The invention relates to a linear light source, and more particularly, to a linear light source having a light guide bar with a sloped and notched light emitting surface and an external reflective housing, which enhances uniformity of beaming light within the beaming light's effective focal range in addition to the overall improvements on light intensity and uniformity.
2. Description of the Prior Art
Scanners, facsimile machines and multifunction peripherals are popularly used in daily life. This type of equipment generally utilizes a linear light source to illuminate the target. Imaging quality of the scanned target is greatly related to the performance of the light source. If the intensity or uniformity of the light source is patchy, the output picture will not be accurate. Under certain circumstances, if the scanned target is not in a fixed focal range and exceeds the effective focal range tolerance of the light source, the output picture will be indistinct. Hence, the light source of the present invention with the overall intensity and uniformity improvements and in particular the uniformity of beaming light within beaming light's effective focal range enhancement has been developed.
Conventional linear light sources are generally cylindrical, square or rectangular. These designs are easier to be molded or fabricated, but the efficiency of light propagation in terms of diffusion and scattering or uniformity control is limited. As a result, many different inventions have been disclosed to resolve these problems. For giving consideration to linear light source designs having a symmetrical polygonal cylinder, the applicant has previously developed a linear light source having a reflecting plane. As shown in FIG. 1, the light source comprises a light guide bar 40′ and a light source component 50′. The light guide bar 40′ is a polygonal cylinder, and includes an arced emission plane 42′, a reflecting plane 44′ corresponding to the arced emission plane 42′, an incidence plane 46′and a plurality of reflecting sides 48′. With this kind of design, the light guide bar 40′ can yield uniformed light with the reflecting plane 44′ after directing the light from the light emitting diode on the light source component 50′. Also, the condensing effect of the arced emission plane 42′ can lead to better light output and enhance the image detecting quality.
The above-mentioned prior art utilizes the plane treatment of the light guide bar to improve the light uniformity, and changes the structure of the light guide bar to improve the condensing effect and light intensity. Although the prior art provides acceptable results, greater improvements are still sought after to optimize the energy conservation, improve the intensity and uniformity of the emitted light, and enhance the uniformity of beaming light within beaming light's effective focal range. Hence, the present invention discloses a linear light source having a sloped and notched light-emitting surface and an external reflective housing which enhances uniformity of beaming light within the beaming light's effective focal range. The reflecting housing with reflecting flange efficiently guides the light and reduces the energy loss with repetitive diffusion and scattering, thus further enhancing the light intensity.